: During setup, sign in with the same Microsoft Account used previously.
: It uses a process called HWID (Hardware ID) activation. It tricks the Windows servers into thinking the machine is eligible for a free upgrade from a previous OS, generating a permanent, legal digital license on Microsoft’s own servers. how-to-activate-windows-10-for-free-in-a-legal-way-aug-2022
If you previously had a legal copy of Windows 10 on your computer but reinstalled it, you don't need a key. : During setup, sign in with the same
If you have an old laptop or a retail box for Windows 7, 8, or 8.1, you can often use that 25-character key to activate Windows 10. : Press Windows Key + I . Update & Security : Select Activation . Change Product Key : Enter your old Windows 7 or 8.1 key. If you previously had a legal copy of
: You can actually use Windows 10 forever without activating it. You will have a "Activate Windows" watermark and lose "Personalization" settings (like changing your wallpaper), but the OS remains functional and receives all security updates.